EP3009823A1 - Method and device for detecting defects in rotor blades - Google Patents

Abstract

The invention relates to a method and a device for detecting defects in rotor blades (1), which have been produced in laminate construction with a layer structure with fiber mats and / or sandwich materials in a plastic matrix, wherein the rotor blade (1) with a on the rotor blade (1 ) is locally heated, the heated spot is detected by a thermal imaging camera (3) guided along the rotor blade (1), and irregularities in the thermal image are output by methods of image processing or signal analysis, wherein the heat radiator (2) and the thermal imaging camera (3) on at least one holder (5) are arranged, which is pressed during the heating and detection against the rotor blade (1).

Description

The invention relates to a method for detecting defects in rotor blades, which have been produced in laminate construction with a layer structure with fiber mats and / or sandwich materials in a plastic matrix, wherein the rotor blade is heated locally with a guided along the rotor blade heat radiator, the heated point with a is detected on the rotor blade guided thermal imaging camera and the nonuniformities in the thermal image are output by methods of image processing or signal analysis. The invention also relates to a device for detecting defects in rotor blades, which have been produced in laminate construction with a layer structure with fiber mats and / or sandwich materials with a plastic matrix, with a heat radiator along the rotor blade and a heat imager tracked thermal imager, with an evaluation is coupled. The laminate structure can also be made exclusively of fiber mats or sandwich materials. Likewise, the laminate construction can be made of fiber mats with localized sandwich materials. Both the method and the device are in particular for the investigation of rotor blades of large wind turbines provided and suitable.

Wind turbine blades may be over 75 m in length and over 15 t in mass. Most rotor blades are made of glass or carbon fiber reinforced plastic in the so-called half-shell sandwich technique, in which the rotor blade half shells are initially produced separately and then glued together with epoxy resins or polyurethane. In the manufacture of the rotor blade half shells, different methods may be used, e.g. the infusion technique, in which fiber mats are soaked in the mold at low pressure with synthetic resin. In another method, prepregs are used in the form of resin-wetted fiber mats with which the mold is lined.

Serious damage to the half-shells or rotor blades can occur in both hand laminates and in vacuum infusion processes of fiber webs, if the fibers, which are only extremely stress-resistant, have been laid parallel to one another in waves or folds. It then creates so-called wrinkles or ondulations. In operation, then the immense tensile forces at peak peripheral speeds of more than 200 km / h must not be absorbed by the fibers, but by the adhesive or the resin matrix. The consequences of such a faulty fiberglass layer, especially in load-bearing belt areas, are cracks or cracks in the massive fiber layer, but also in the leaf shells, which can possibly lead to complete destruction of individual leaves.

Since fiber fabric, in particular glass fiber fabric or carbon fiber fabric, by the inherent stiffness and the always given rounded surface shape of the rotor blade when designing the form can always have only an approximate planarity, angular deviations in the orientation of the scrim or tissue can not be avoided. It is important how affected areas of impermissibly high angular deviations can be detected without a destructive examination.

There are point measuring devices that use ultrasonic exciters or a microwave technique. The principle possibility of finding an ondulation with a width of 5 mm is given by such punctually measuring methods, however, the point measuring methods with rotor blade surfaces of more than 200 m ² lead to an extremely time-consuming test.

An alternative apparatus and method for inspecting rotor blades of a wind turbine is disclosed in US Pat DE 10 2010 046 493 B3 described in which the rotor blade to be tested is heated by means of an excitation source in the form of a deflection and focusing system. Sunbeams are focused by a deflecting mirror and directed to the rotor blade. The mirror is mounted on a flying carrier which flies along the rotor blade at a controlled distance. An infrared sensor may be stationed firmly on the ground or attached to the flying carrier together with the excitation source. The flying carrier works at a constant speed along the rotor blade to be tested. This technique requires the presence of sunshine, which is not always the case. If the sun shines, it hinders the detection of the IR radiation emitted by the rotor blade through the thermal imaging camera.

From these thermographic measurements, the location of the defect or ondulation can be determined cost-effectively, if necessary, even existing consequential damage can be found. The two-dimensional test achieves a significant reduction in the test duration compared to punctiform measuring devices or methods. Destructive testing of the rotor blades need not be performed, but can be checked by the non-destructive material testing a large number of rotor blades in use, so in the assembled state, which prevents major leaf losses can be.

A disadvantage of the known method and the known device is that high inaccuracies in the heating as well as the detection of the thermal image arise because an aircraft with a deflection mirror provides no guarantee for uniform heating and a uniform measurement distance.

The object of the present invention is to provide a device and a method for detecting defects in rotor blades, which have a higher accuracy compared to the known method and the known device in order to more precisely determine the location of the defect, the ondulation and also the extent of the defect to be able to.

According to the invention this object is achieved by a method having the features of the main claim and a device having the features of the independent claim. Advantageous embodiments and further developments of the invention are disclosed in the subclaims, the description and the figures.

The inventive method for detecting defects in rotor blades, which have been produced in laminate construction with a layer structure with or from fiber mats and / or sandwich materials in a plastic matrix, wherein the rotor blade is heated locally with a guided along the rotor blade heat radiator, the heated point with a detected on the rotor blade along thermal imager and emitted irregularities in the thermal image with methods of image processing or signal analysis, provides that the heat radiator and the thermal imager are arranged on at least one holder, which is pressed during the heating and detection by the thermal imager against the rotor blade , The holder on which the thermal imaging camera or the heat source or the heat radiator are arranged, is guided along the surface of the rotor blade, wherein the holder is pressed against the rotor blade surface, so that there is always a contact between the holder and the rotor blade, so that due to the fixed geometric assignment of the holder to the heat radiator and the thermal imager always a constant distance can be maintained. This makes it possible to irradiate each surface of the rotor blade to be examined with a defined, consistent and reproducible amount of heat and also to guide the thermal imaging camera over the irradiated area at a defined distance to a precise, spatially resolved representation of the emitted heat radiation and the inhomogeneities in determine the heat radiation of the investigated rotor blade. On the basis of the inhomogeneities of the detected thermal radiation, inhomogeneities in the structure of the rotor blades can be concluded. In addition, it is possible, for example, using a run along the rotor blade platform, the surface of the rotor blade at the reference immediately aufschleleifen, visually inspect and possibly repair immediately.

The at least one holder can be pressed pneumatically, hydraulically or by way of a mechanical energy store or also by means of the weight force with a pretensioning device against the rotor blade. The defined application of force ensures that there is always contact between the holder and the rotor blade.

On the holder, a contact surface or a contact roller is arranged, which is guided along the surface of the rotor blade. The contact surface may be provided with a reduced-friction coating, so that the surface of the rotor blade is not damaged. An embodiment as a contact roller reduces the frictional resistance and the ability to damage the surface by testing the rotor blade.

The heat radiator and the thermal imaging camera are preferably moved at a constant distance from the rotor blade surface in order to rule out that measurement inaccuracies occur due to distance fluctuations.

The at least one holder can be guided on a fixed path along the rotor blade or the rotor blade steering axis, which is particularly suitable for a check during and after production in the non-installed state. The measuring device with the heat radiator can be moved on a rail guide along the rotor blade with a uniform, predetermined speed, for example, wherein distance fluctuations due to the curvature of the rotor blade or alignment error by the contact pressure, which presses the holder against the rotor blade, are compensated. For this purpose, the holder can be arranged displaceably on a working platform or the like, wherein due to the change in length of the holder no change in the distance from the heat radiator and the thermal imaging camera to the rotor blade occurs, or if these components at the front part of the holder at a fixed distance to attached to the front end of the holder.

In order to further reduce inaccuracies, the thermal imager is tracked at a constant distance from the heat radiator, so that at a constant travel speed of the heat radiator along the rotor blade between the irradiation and the recording is always the same period, so that a reproducible result can be provided.

Advantageously, the orientation of the thermal imager as well as the heat radiator of the surface contour of the rotor blade is adjusted. For this purpose, the thermal imaging camera and the heat radiator are always kept oriented perpendicular or at a constant angle to the surface of the rotor blade, so that the change in the shape of the rotor blade is also taken into account in the transverse direction. The thermal imaging camera and the heat radiator can be tracked, which makes a corresponding articulated mounting on the holder or a bracket required.

A development of the method provides that the position of the thermal imaging camera and / or the heat radiator on the rotor blade is detected and assigned to the thermal image data. The position of the thermal imaging camera, the heat radiator or both components on the rotor blade is advantageously measured from a reference point, for example from the starting point of the measurement, for example at the attachment point of the rotor blade to the hub. The path traveled from there is assigned to the respective images which are taken by the thermal imaging camera, for example burned in or stored in parallel, so that a simple retrievability of the respectively examined location on the basis of the evaluated thermal image data is easily possible. If a certain point detected as faulty, this point can be easily recovered, for example, in the context of maintenance, so that the detection of defects and their correction can fall apart in time.

The images with detected errors are advantageously stored separately in an error file, preferably with the position data, so that not the entire thermographic evaluation of the rotor blade has to be evaluated for the correction of defects.

The device for detecting defects in rotor blades, which have been produced in laminate construction with a layer structure of fiber mats in a plastic matrix, with a heat radiator along the rotor blade and a heat tracker tracking thermal imager coupled to an evaluation, provides that the Heat radiator and the thermal imaging camera are arranged on at least one holder, which is associated with a biasing means for pressing the holder against the rotor blade. By the biasing means of the holder against the rotor blade pressed and held on the rotor blade when passing over the surface of the rotor blade, in particular along the longitudinal extent of the rotor blade, so that changes in the shape of the rotor blade in the transverse direction can be followed.

A development of the invention provides that the at least one holder is mounted displaceably on a working platform, so that the distance from the heat radiator or the thermal imaging camera to the rotor blade or to each other is adjustable. In addition, on the one hand, the holder of the holder can be secured to the working platform via a holder, which is telescopic, for example, and on the other hand, the working platform are moved on a path relative to the rotor blade, which does not run parallel or equidistant from the rotor blade contour. In addition, the adjustability of the distance of the thermal imager and the heat radiator by an adjustability of the holder relative to the surface of the rotor blade is possible.

The thermal imaging camera can be mounted displaceably relative to the heat radiator, in particular on a working platform, so that on the one hand the distance in the direction of displacement of the heat radiator or the thermal imaging camera is given, as the change of the distance from the thermal imager to the rotor blade and the heat radiator to the rotor blade , The greater the distance of the thermal imaging camera to the heat radiator in the direction of displacement, the greater the time interval with which the thermal imaging camera takes the corresponding image, whereby errors in comparatively great depths of the rotor blade structure can also be detected. A slow travel speed or a large distance between the heat radiator and the thermal imager increase the depth range of the technique and the method. The greater the distance of the thermal imager to the surface of the rotor blade, the lower the amount of heat that can be absorbed by the camera, so that an adaptation to the sensitivity of the thermal imager by the adjustability of the distances is possible.

In order to be able to align the orientation of both the thermal imaging camera and the heat radiator uniformly relative to the surface of the rotor blade, the heat radiator and / or the thermal imaging camera is advantageously mounted displaceable on the at least one holder, so that, for example, always an orthogonal orientation of the thermal imaging camera and the heat radiator can be ensured to the rotor blade surface. The displaceable mounting can be done for example via a ball joint, a universal joint or another multi-axis joint that allows a shift in several degrees of freedom.

The at least one holder can be displaceably mounted along a fixed path, for example along a rail which is oriented alongside and advantageously parallel to the longitudinal extent of the rotor blade to be examined. For example, the work platform can be mounted on a carriage, so that both the thermal imaging camera and the heat radiator can be moved at a constant or almost constant speed along the rotor blade. The work platform can be attached to two ropes, which are either pulled over the two blades not to be examined and are attached to or in the gear housing. One or more motors operating synchronously, for example mounted above the work platform, raise or lower the work platform. The travel speed of the work platform is adjustable so that speed can influence the depth range of the examination.

In addition to a pivotable mounting of the thermal imaging camera and / or the heat radiator on the holder, these can also be arranged displaceably on the holder in order to ensure adjustability of the distances from each other and the rotor blade surface.

The device may be associated with a measuring device, with which it is possible to detect the position of the thermal imager on the rotor blade. The measuring device can be designed as a GPS-based sensor device, as a counting wheel or as an evaluation device of a measured travel speed of the thermal imaging camera. Via the measuring device it is possible to determine the position of the thermal imaging camera on the rotor blade and to assign this location data to the respective acquired thermal images. In this case, the measuring device by means of external reference data via a satellite-based positioning system work, so that regardless of the distance covered a position of the measuring device and thus the thermal imaging camera can be assigned. The prerequisite for this is likewise to determine the position of the rotor blade or to determine at least one defined orientation of the rotor blade during the measurement, for example in a vertically downwardly oriented position. A mechanical measuring device may represent a counting wheel or a comparable displacement measuring device, which is preceded or tracked from the beginning of the measurement, for example on the hub, of the thermal imaging camera, so that the position can be determined from an initial position. As an alternative to a counting wheel, it is also possible to set up an optical measuring device, for example a laser measuring system. It is also possible, based on the data of the engine control, which is used to move the measuring device or the thermal imaging camera along the rotor blade, derive the trajectory over the traversing speed and the travel time or to calculate based on the speed and the translations, at which position of the rotor blade respective measurement has taken place at a certain time and assign this position data to the image.

Figur 1 -

ein Rotorblatt in einer Gesamtansicht;

Figur 2 -

eine vergrößerte Schnittdarstellung eines Gurtlaminats;

Figur 3 -

eine schematische Darstellung einer Untersuchung; sowie

Figur 4 -

eine schematische Einzeldarstellung einer Vorrichtung.

Hereinafter, an embodiment of the invention will be explained in more detail with reference to the accompanying figures. Show it:

FIG. 1 -

a rotor blade in an overall view;

FIG. 2 -

an enlarged sectional view of a Gurtlaminats;

FIG. 3 -

a schematic representation of an investigation; such as

FIG. 4 -

a schematic single representation of a device.

In the FIG. 1 is shown in a schematic representation of a rotor blade 1 of a wind turbine with a belt 10, which serves as a supporting structure of the rotor blade 1. The rotor blade 1 has a curved surface to obtain a wing-like structure. The rotor blade 1 and in particular the belt 10 are made of a laminate of fiber mats, for example glass fiber mats or carbon fiber mats, which are embedded in a plastic matrix, for example an epoxy resin or the like. The fiber fabric is placed for shaping, for example, in a template and impregnated with the application of negative pressure with resin. The fibers themselves are designed to absorb very high tensile forces, the plastic or resin matrix is used to assign the fiber orientations to each other, for fixing the scrim and their protection against mechanical and chemical effects.

FIG. 2 shows the cut-out belt 10 as Gurtlaminat and supporting structure with a wave shape or ondulation 12 in the area in which the fabric or fiber mats are not uniformly linear everywhere, but only partially offset at an angle to each other, laid in a wave or in a fold. The resulting cavity between the fiber layers or on the surface is filled with the resin, so that there are different internal structures in the field of faulty laying of the fiber mats. It happens that in the area of the fillings accumulate bubbles, which are also very well detected by a thermal imaging camera. Due to the different thermal conductivity of the resin relative to a Mixture of resin and fiber fabric may result in a thermographic examination to different thermographic images, if a uniform heating of the rotor blade 1 or a portion of the rotor blade 1, for example, the belt 10 takes place. Since the heat introduced by a heat radiator can not be dissipated so well by the resin or the air deposits, a brighter picture results in the area of the defects, while with a correct or even laying of the fabric layers a uniform, relatively dark image is detected can be.

FIG. 3 shows a schematic representation of the rotor blade 1 and the working platform 4, which is fixed to the rotor blade 1. The work platform 4 is in the FIG. 4 shown in an enlarged detail. To carry out the test method, a heat radiator 2 and a thermal imaging camera 3 are attached to the work platform 4. The heat radiator 2 is supplied via an external energy source, in particular supplied with electricity, so that the heat radiator converts the electrical energy into heat energy. The optics of the thermal imager 3 are set such that the areas heated and to be examined by the heat radiator 2, for example the area of the heat radiation device 2 Belt 10, can be sharply imaged. The thermal imaging camera 3, like the heat radiator 2, is attached to a respective holder 5, at the front end of which in each case a contact roller 6 is fastened, which rolls on the surface of the rotor blade 1.

In the presentation of the FIG. 3 the working platform 4 is located on a cable which is fastened, for example, to the hub of a rotor of the rotor blade. About the rope, the vertically downward-standing rotor blade 1 can be checked in the assembled state. The work platform 4 is lowered down to the rotor blade 1, wherein a force F is exerted in the direction of the rotor blade 1, for example via a pneumatic or mechanical pressure. The contact rollers 6, at a fixed, constant distance from both the heat radiator 2 and the thermal imager 3 are mounted so as not to disturb the heating and the image field, roll constantly on the rotor blade 1 from. Between the heat radiator 2 and the thermal imaging camera 3, a fixed distance D is set, which is changeable via the displaceable mounting of the heat radiator 2 on a boom 7 of the holder 5. Likewise, the positions of the heat radiator 2 and the thermal imaging camera 3 along the longitudinal extent of the holder 5 are changeable, which is indicated by the double arrows.

While the work platform 4 is moved along the rotor blade 1 at a predefined, adjustable, constant speed, infrared images or videos of the heat distribution of the surface of the rotor blade 1 are taken by the thermal imaging camera 3 and transmitted to an evaluation device, not shown. The heat radiator 2 can be embodied as a line-shaped jet or area radiator and is arranged in front of the thermal imaging camera 3 in the direction of travel during the examination for defects. Due to the changing radiation at changing densities due to delmamination, angular distortion, wrinkles or the like, heat differences can be detected by the thermal imager 3, so that air pockets and resin accumulations can be detected as warmer spots with the thermal imager 3.

For the optical control and a possibly necessary repair of individual sections of rotor blades 1 of a wind turbine, the working platforms 4 are used, which may also comprise the entire rotor blade 1 and are guided by the rotor blade 1. The heat radiator 2 is mounted in the illustrated embodiment on the underside of the work platform 4, so that the surface of the rotor blade 1 can be heated linearly and substantially orthogonal to the blade longitudinal axis. As a result, the surface is heated homogeneously at a uniform travel speed in the test direction by the heat radiator 2. This is achieved in that the heat radiator 2 always the same distance to the rotor blade. 1 holds. For the tracking of the thermal imaging camera 3 and the heat radiator 2 in a change in the shape of the rotor blade in the transverse direction along its longitudinal extent, both the heat radiator 2 and the thermal imager 3 is pivotable, for example, gimbaled, so that always a constant, usually orthogonal orientation both the heat radiator 2 and the thermal imaging camera 3 is ensured relative to the surface of the rotor blade 1.

In the FIG. 4 are also the biasing means 5a, 5b shown, which exert a force in the direction of arrow on the respective holders, so that they are pressed against the rotor blade 1. The biasing means 5a, 5b may be spring means, motors, accumulators or similar means biasing the respective components of the apparatus against the rotor blade 1. The working platform 4 may have on the respective rear side of the rotor blade a re-storage, for example in the form of a roller which is guided on a linkage, so that the holder can additionally be supported against the rotor blade 1.

Claims (16)

Method for detecting defects in rotor blades (1) which have been produced in laminate construction with a layer structure comprising fiber mats and / or sandwich materials in a plastic matrix, the rotor blade (1) being local with a heat radiator (2) guided along the rotor blade (1) is heated, the heated spot detected with a on the rotor blade (1) along thermal imaging camera (3) and output irregularities in the thermal image with methods of image processing or signal analysis, characterized in that the heat radiator (2) and the thermal imaging camera (3) at least one holder (5) are arranged, which is pressed during the heating and detection against the rotor blade (1). A method according to claim 1, characterized in that the at least one holder (5) is pressed pneumatically, hydraulically or via a mechanical energy accumulator with a biasing means (5a, 5b) against the rotor blade (1). A method according to claim 1 or 2, characterized in that on the at least one holder (5) a contact surface or a contact roller (6) is arranged, which is guided along on the surface of the rotor blade (1). Method according to one of the preceding claims, characterized in that the heat radiator (2) and the thermal imaging camera (3) are moved at a constant distance from the rotor blade surface. Method according to one of the preceding claims, characterized in that the at least one holder (5) is guided on a fixed path along the rotor blade (1) or the rotor blade longitudinal axis. Method according to one of the preceding claims, characterized in that the thermal imaging camera (3) is tracked at a constant distance (D) from the heat radiator (2). Method according to one of the preceding claims, characterized in that images with detected errors are stored separately in an error file. Method according to one of the preceding claims, characterized in that the position of the thermal imaging camera (3) and / or the heat radiator (2) on the rotor blade (1) is detected and assigned to the thermal image data. Device for detecting defects in rotor blades (1) which have been produced in laminate construction with a layer structure of fiber mats and / or sandwich materials in a plastic matrix, with a heat radiator (2) which can be guided along the rotor blade (1) and a heat radiator (2) tracked thermal imaging camera (3), which with a Evaluation device is coupled, characterized in that the heat radiator (2) and the thermal imaging camera (3) are arranged on at least one holder (5) to which a biasing means (5a, 5b) for pressing the holder (5) against the rotor blade (1) assigned. Apparatus according to claim 9, characterized in that the at least one holder (5) on a working platform (4) is mounted displaceably. Apparatus according to claim 9 or 10, characterized in that the thermal imaging camera (3) relative to the heat radiator (2) is mounted displaceably. Device according to one of claims 9 to 11, characterized in that the heat radiator (2) and / or the thermal imaging camera (3) are displaceably mounted on the at least one holder (5). Device according to one of claims 9 to 12, characterized in that the at least one holder (5) is displaceably mounted along a predetermined path. Device according to one of claims 9 to 13, characterized in that the thermal imaging camera (3) and / or the heat radiator (2) are pivotally mounted on the at least one holder (5). Device according to one of claims 9 to 14, characterized by a measuring device which detects the position of the thermal imaging camera (3) on the rotor blade (1). Apparatus according to claim 15, characterized in that the measuring device as a GPS-based sensor device, as counting wheel or as evaluation of a measured traversing speed of the thermal imaging camera (3) is formed.

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